The present invention relates to a structural body and to a hollow extruded frame member used to form the structural body by friction stir welding. The invention relates more particularly to a novel joint shape of a structural body formed by joining hollow extruded frame members using friction stir welding.
The present invention relates to a structural body and hollow extruded frame members used in forming the structural body by friction stir welding, and the invention relates particularly to structural members suited to use, for example, as an aluminum alloy member of the type used in a railway vehicle and in building construction.
As described in Japanese application patent laid open publication No Hei. 9-309164 (EP 0797043 A2), a friction stir welding method is a method in which, by rotating a round rod (referred to hereinafter as a rotary body) which is inserted into a joint between hollow extruded frame members to be joined and by moving the rotary body along a line of the joint between the frame members to be joined, the joint of the frame members is exothermally heated and softened and the joint is elastically fluidized to form a solid weld.
The rotary body for carrying out the friction stir welding comprises a small diameter portion which is inserted in the joint and a large diameter portion which is positioned outside the joint. The small diameter portion and the large diameter portion of the rotary body have the same axis. A boundary face portion between the small diameter portion and the large diameter portion of the rotary body is inserted a little into the joint. The welding according to the friction stir welding method may be applied to an abutting portion of two frame members or to an overlapping portion of the frame members.
As disclosed in the above-state publication, a protruding portion of a frame member is provided at the portion of the frame member to be subjected to welding. This protruding portion of the frame member comes into contact with the rotary body, so that the protruding portion of the frame member is welded using the friction stir welding method. As further disclosed in the publication, a protrusion chip is provided at the portion of the frame member to be subjected to welding. This protrusion chip protrudes from a rib of an end portion of one of the hollow extruded frame members to be subjected to welding toward the other hollow extruded frame member to which it is to be joined. On this protrusion chip a face plate of the other hollow extruded frame member is overlapped.
Since friction stir welding is carried out by inserting a rotary body serving as a joining tool into a joint between the hollow frame members to be welded causing metal to be fluidized, a large force is exerted on the frame members during welding. Namely, a large force is required for inserting the rotary body into the joint between the frame members to be welded, and so the frame members must be constructed to endure this large force. As a result, when the hollow extruded frame members are joined, as described in the above-stated publication, metal easily flows to a rear side of the joint. Therefore, it is necessary to make the protruding portion of the hollow extruded frame members rather large for supplementing the amount of metal which flows in the joint. Further, void holes occur easily in a joining bead of the frame members.
As one means for preventing the above-stated various defects, the thickness of the frame member to be subjected to welding is made large at the joint portion, thereby the flow-out of metal from the frame members can be prevented. For example, by giving a large circular arc shape to the corner between the face plate and the rib at the joining portion of the frame member, the thickness of an outer portion of the frame member to be subjected to welding can be increased. Further, for example, by making the diameter of the circular arc shape of the corner between the protrusion chip and the rib of the frame member large, the thickness of the outer portion of the frame member to be subjected to welding can be increased.
The above stated circular arc shape of the frame member to be subjected to welding is recessed toward a side of the face plate of the frame member. Accordingly, the cross sectional area of the frame member to be subjected to welding becomes large, with the result that the weight of the frame member increases.
An object of the present invention is to provide a structural body wherein a light weight joint member or light weight joining portion of the structural body can be attained and to provide a hollow extruded frame member wherein a light weight joint member or a light weight joining portion of the hollow extruded frame member can be attained.
Another object of the present invention is to provide a structural body having a small cross-sectional area and a hollow extruded frame member having a small cross-sectional area which can be easily and effectively welded using friction stir welding.
The above stated object can be attained by shaping the corner between a rib at a vicinity of a joining portion and a face plate of a hollow extruded frame member or a corner between a protrusion chip and a rib of the hollow extruded frame member in the form of a circular arc which protrudes outwardly from the corner at the center thereof, namely a circular arc which protrudes toward an inner hollow portion of the hollow extruded frame member.
According to the present invention, a structural body is characterized in that it is formed of a first member having two substantially parallel first face plates and plural first ribs for connecting the two first face plates, and a second member having two substantially parallel second face plates and plural second ribs for connecting the two second face plates, wherein the first member and the second member are joined by two joining beads, one of the two joining beads joins one of the two first face plates of the first member to one of the two second face plates of the second member, the other of the two joining beads joins the other of the two first face plates of the first member and the other of the two second face plates of the second member. In accordance with the present invention, a corner between the first rib of the first member in the vicinity of one of the two joining beads and a rear face of the one of the two first face plates of the first member at a position of a first hollow portion of the first member is in the form of a first circular protruding arc which extends into the first hollow portion of the first member.
According to the present invention, a structural body is characterized in that it is formed of a first member having two substantially parallel first face plates and plural first ribs for connecting the two first face plates, and a second member having two substantially parallel second face plates and plural second ribs for connecting the two second face plates, wherein the first member and the second member are joined by two joining beads, one of the two joining beads joins one of the two face plates of the first member to one of the two second face plates of the second member, the other of the two joining beads joins the other of the two first face plates of the first member and the other of the two second face plates of the second member. In accordance with the present invention, the two joining beads are positioned respectively at an intermediate portion between a first rib of the first member and a second rib of the second member in the vicinity of the joint, and one of the two second face plates of the second member overlaps a protrusion chip which protrudes from the first rib in the vicinity of the one of the two joining beads toward the second member. Further, the corner between the first rib in the vicinity of the one of the two joining beads and a rear face of one of the first face plates at a position of a hollow portion of the two first members is in the form of a circular protruding arc which extends into the hollow portion of the first member, and a corner between the second rib in the vicinity of the one of the two joining beads and a rear face of one of the two second face plates at a position of a hollow portion of the second member is in the form of a circular protruding arc which extends into the hollow portion of the second member.